A Hybrid Model for Predicting Steering Brake Squeal Based on Multibody Dynamics and Finite Element Methods

In recent years, the problem of automotive brake squeal during steering braking has attracted attention. Under the conditions of squealing, the loading of sprung mass is transferred, and lateral force is generated on the tire, resulting in stress and deformation of the suspension system. To predict the steering brake squeal propensity and explore its mechanism, we established a hybrid model of multibody dynamics and finite element methods to transfer the displacement values of each suspension connection point between two models. We successfully predicted the occurrence of steering brake squeal using the complex eigenvalue analysis method. Thereafter, we analyzed the interface pressure distribution between the pads and disc, and the results showed that the distribution grew uneven with an increase in the steering wheel angle. In addition, changes in the contact and restraint conditions between the pads and disc are the key mechanisms for steering brake squeal.

Parametric Study of Track Support Structure to Minimize the Occurrence Possibility of Rail Corrugation

Changing the track support structure is an effective method to suppress or eliminate rail corrugation in practical engineering. Rail corrugation on small-radius curves with booted short sleepers is the main research object in the present paper. A relevant finite element model of the wheelset-track system supported by booted short sleepers is built combined with the dynamic analysis of the vehicle-track system. The effects of various parameters of booted short sleeper structure on the wheel–rail friction-induced vibration are investigated by complex eigenvalue analysis. Considering the interaction of multiple parameters in the booted short sleeper structure, the multi-parameter fitting equation forecasting the possibility of rail corrugation is obtained using the least squares algorithm. Results show that wheel–rail friction-induced oscillation is a contributing factor in the formation of rail corrugation. Controlling wheel–rail friction-induced oscillation with a frequency of about 300 Hz is beneficial to suppress the possibility of rail corrugation in sections with booted short sleepers. Lower fastener stiffness or greater vertical fastener damping make it less likely that rail corrugation will occur. Rail corrugation is not generated when the vertical stiffness of the fastener is controlled below 20 MN/m in the booted short sleeper.

The Basin Stability of Bi-Stable Friction-Excited Oscillators

Stability considerations play a central role in structural dynamics to determine states that are robust against perturbations during the operation. Linear stability concepts, such as the complex eigenvalue analysis, constitute the core of analysis approaches in engineering reality. However, most stability concepts are limited to local perturbations, i.e., they can only measure a state’s stability against small perturbations. Recently, the concept of basin stability was proposed as a global stability concept for multi-stable systems. As multi-stability is a well-known property of a range of nonlinear dynamical systems, this work studies the basin stability of bi-stable mechanical oscillators that are affected and self-excited by dry friction. The results indicate how the basin stability complements the classical binary stability concepts for quantifying how stable a state is given a set of permissible perturbations.

Correlation of Short Pitch Rail Corrugation with Railway Wheel-Track Resonance at Low Frequencies of Excitation

As much as there has been a significant increase in the development of railway systems in recent years, one of the significant drawbacks on this mode of transport is ground-borne vibrations and noise emanating from vehicle-track interaction in service. This greatly affects the ecology and physical surroundings of the railway track. Experimental tests and Finite Element modal and complex eigenvalue analysis are conducted to investigate the dynamics of a traction wheelset and rail track. This is done to establish the correlation between the short pitch rail corrugation in the Belfast to Steelpoort railway line, in the Limpopo Province of South Africa, with railway wheel-tract resonance at low frequencies of excitation. A 3D Finite Element Method (FEM) and complex eigenvalue analysis are used to validate the resonance modes of the wheelset and rail track obtained through experimental modal analysis. Mode shapes are determined for natural frequencies that match the excitation frequency induced by short pitch rail corrugation. The results show that based on average train speeds around track curves, the excitation frequency induced by corrugation matches (quite reasonably) natural frequencies of the wheelset. Whilst the wheelset FEM results are in better agreement, they rather prove the correlation to occur at 100 Hz. In a previous study by the authors, at the average speeds per track curve, the corrugation excitation frequency was found to be 108 Hz. The current study goes further by investigating natural frequencies of rail tracks. Moreover, mode shapes of a traction wheelset and rail tracks are also investigated, and the results are presented herein.

Stability Improvement of Brake Disc to Mode Coupling at High Frequency Squeal

In this research study, the high-frequency squeal noise of a brake disc was found to occurred at a frequency of about 15 kHz. The potential root cause has been studied where mode frequency coupling and shape locking mechanism of brake disc and brake pads components are the main investigated topic. From the vehicle field test and the Dynamometer test, the braking condition, friction coefficient and braking pressure, have been confirmed to be used in numerical experiments. The updated finite element model (FEM) with the modal testing data of the existing brake components are formulated for the Complex Eigenvalue Analysis (CEA). In this study, the modification is based on in-board and out-board cheek thickness of the brake disc. Two of nine modifications of the brake disc cheek thickness are proposed with the method of separation the brake disc out-of-plane and in-plane modes and the method of avoiding shape locking between the brake disc and the brake pads modes. The constructed prototypes are verified with the vehicle field test and well agreed with the CEA.

The Basin Stability of Bi-Stable Friction-Excited Oscillators

Stability considerations play a central role in structural dynamics to determine states that are robust against perturbations during the operation. Linear stability concepts, such as the complex eigenvalue analysis, constitute the core of analysis approaches in engineering reality. However, most stability concepts are limited to local perturbations, i.e. they can only measure a state’s stability against small perturbations. Recently, the concept of basin stability has been proposed as a global stability concept for multi-stable systems. As multi-stability is a well-known property of a range of nonlinear dynamical systems, this work studies the basin stability of bi-stable mechanical oscillators that are affected and self-excited by dry friction. The results indicate how the basin stability complements the classical binary stability concepts for quantifying how stable a state is given a set of permissible perturbations.